1. Field of the Invention
The present invention generally relates to a method and system for patterning of thin films, and more particularly to a method and system for patterning magnetic thin films using gaseous transformation.
2. Description of the Related Art
Patterning of thin magnetic films for application in various sensors and devices, such as thin-film disk drive read heads and magnetic memory elements, has relied on removal (e.g., physical removal) of material by reactive ion etching (RIE), ion milling and other subtractive techniques.
Hence, these methods use physical removal of material in order to delineate a region both magnetically and electrically. Typically, the region to be patterned is of micron or submicron dimension, and often sensitivity to edge roughness, profile and redeposited material determines the quality of the final product.
Recently, experiments (e.g., see W. H. Bruenger et al., “Ion Projection Lithography for Resistless Patterning of Thin Magnetic Films”, 25th International Conference on Micro and Nano Engineering, Rome, Italy, 21-23 Sep. 1999 and Microelectronics Engineering (Netherlands) Vol. 53, No. 1-4, June 2000, pp. 605-608; and B. D. Terris et al., “Patterning Magnetic Films by Ion Beam Irradiation”, Journal of Applied Physics (USA), Volume 87, No. 9 pt. 1-3, 1 May 2000, pp. 7004-7006) have used ion beams to pattern (e.g., by damage and by implantation) without physical removal of material. Specifically, such a method has used an oxygen implantation technique. However, prior to the invention, such a technique has not been applied to magnetic memory devices.
In the case of magnetic memory (MRAM) structures, patterning of the tunneling junction device as discussed above is of utmost importance in achieving final success and a high-performance product.
Mainly, the failure of the final product is due to non-uniformity of magnetic switching properties in the potentially millions of junctions on a memory chip. This variability is traced to many different factors, but one of the most important is in the patterning process. Gross differences in shape lead to a variation in the magnetic switching field. Also, edge roughness is known to cause variation due to edge pinning of magnetization.
Finally, magnetic hardening of the edges due to oxidation, edge thinning, and magnetic effects due to redeposited material each influence magnetic performance. In all of the patterning methods in which removal of material is used (e.g., ion milling, reactive ion etching (RIE), etc.), the edges of the patterned area are compromised in at least one of these ways.
Thus, ion-beam patterning (as opposed to ion milling) offers significant promise for improved performance but remains unproven.
However, as mentioned above, while the conventional methods may have attempted oxygen implantation for oxidation patterning, such has not been attempted with MRAM devices, nor has there been any patterning of MRAM devices by exposure to a reactive plasma, let alone by using fluorination.